This application relates to and incorporates by reference Japanese patent application no. 2001-153094, which was filed on May 22, 2001, and Japanese patent application no. 2001-153095, which was filed on May 22, 2001.
The present invention relates to a variable displacement compressor in which the theoretical discharge rate (the flow rate determined by stroke and bore diameter) is changed by changing the strokes of a plurality of reciprocating pistons. This is done by changing the inclination of an inclining member, such as a swash plate or an oscillating plate, which is inclined relative to the axis of a shaft. Variable displacement-compressors are suited for a vapor-compression type refrigeration cycles for vehicles (vehicle air conditioners).
A variable displacement compressor disclosed in Japanese unexamined patent publication (JP-A) no. Sho 62-225782 includes an elongated linking groove (linking aperture) at the front side of an arm that extends radially from a shaft. The inclining member is linked to the arm such that oscillation of an inclining member is possible due to a link pin passing through the linking groove.
When assembling the variable displacement compressor, it is necessary to install the inclining member on the arm while a plurality of pistons is connected to the inclining member. However, the size of the crankcase (housing) is usually made no larger than necessary for accommodating the inclining member, because it takes more time to change the pressure inside the crankcase when the size (volume) of the housing (especially, the crankcase accommodating the inclining member) increases. Thus, it is difficult to install the inclining member, because the freedom of movement of the inclining member is, in general, comparatively low during the installation.
With regard to variable displacement compressors that change the inclination angle of an inclining member, such as a swash plate or an oscillating plate, the inclination angle of the inclining member is generally controlled by controlling the pressure inside a swash plate chamber (crankcase), as disclosed in Japanese unexamined patent publication (JP-A) No Sho. 62-203980 or Japanese unexamined patent publication (JP-A) No. Sho. 62-240482.
The capacity of the swash plate chamber (crankcase) is comparatively large, since it accommodates the inclining member. As a result, a comparatively large amount of gas is needed to control the pressure inside the crankcase (this pressure is referred to as the control pressure), and there is a comparatively large time lag until the actual control pressure changes, subsequent to the actuation of the control valve (the control signal of the control valve) that controls the control pressure.
Therefore, there is a delay in response until the theoretical discharge flow rate, or displacement, actually changes, and it is difficult to control the displacement with precision.
Blow-by gas (gas leaking between the cylinder bores and the pistons) flows into the crankcase, and this problematically changes the displacement (decreases the displacement) even though the control valve has not been activated, by increasing the pressure inside the crankcase. Thus, there is a need for a compressor that is more responsive to controls.
The present invention was made in view of the above-mentioned problems, and it is an object of this invention to improve assembly, when connecting an inclining member, with a plurality of pistons attached, to an arm. It is a further object to provide a compressor with improved responsiveness.
In order to accomplish these objects, one aspect of the present invention provides a variable displacement compressor that changes a theoretical discharge by changing strokes of a plurality of reciprocating pistons (112), which in turn is done by changing an inclining member (108, 110) inclined relative to a center axis (L0) of a shaft (106), and by changing an inclination angle (xcex8) between the centerline (L0) and the inclining members (108, 110). The variable displacement compressor is provided with a housing (101, 102, and 105) that accommodates the shaft (106) and the inclining member (108, 110), and the housing is also provided with a plurality of cylinder bores (103) for accommodating the pistons (112). The variable displacement compressor is also provided with an arm (106a), onto which the inclining member (108, 110) is linked, such that the inclining member (108, 110) can move radially from the centerline (L0), and which transmits rotating force of the shaft (106) to the inclining member (108, 110). A coupling between the arm (106a) and the inclining member (108, 110) includes a linking groove (108b) provided on one of the arm (106a) and the inclining member (108, 110), and a link pin (109) fixed on the other of the arm and the inclining member, such that the pin can slide within the linking groove (108b). The linking groove (108b), is open, with an opening (108c) provided at one end of the linking groove.
As a result, the assembly process is easier, because it is possible to easily connect the inclining member (108, 110), when a plurality of pistons (112) is attached to, the arm (106a), by inserting the link pin (109) into the linking groove (108b), from the opening portion (108c) of the linking groove (108b), even when the degree of freedom in movement of the inclining member is relatively restricted.